Cytokinesis is the process by which a cell divides into two daughters. When mitosis is complete, a cleavage furrow assembles in the middle of the cell and this furrow constricts to divide the cell into two equal parts. Cytokinesis is fascinating from a basic cell biology perspective, since it requires concerted activity of the cytoskeleton and membrane systems of the cell. It is also a process that could potentially be targeted in anti-cancer therapy. We are interested in two questions: how does the cell position the cleavage furrow exactly in its middle and how does the furrow assemble? We will address these by a combination of biochemistry, microscopy and addition of drugs. We will continue our biochemical analysis of two interesting cleavage furrow proteins, anillin, which we discovered, and septins, a family of GTPase proteins that we showed could assemble into filaments. We want to know what these proteins do in the cell and how they influence each other. We will study how new membrane is targeted to the cleavage furrow using extracts from frog eggs and the role of anillin in this process. Building a furrow at the center of the cell depends on microtubules that provide the positional information. We will probe how the microtubules associated with cytokinesis are organized in the cell and what mechanisms they use to target anillin and myosin II to the center of the cell to build a furrow there.